[Property wrappers] Sync up implicit "nil" initialization defaulting.

Perform implicit "nil" initialization for a wrapped property only when
the memberwise initializer's parameter is of the wrapped type.

Author: DougGregor

lib/AST/Decl.cpp

@@ -5830,7 +5830,7 @@ bool VarDecl::isPropertyMemberwiseInitializedWithWrappedType() const {
   if (getAttachedPropertyWrapperTypeInfo(0).defaultInit)
     return false;
 
-  // If all property wrappers have an initialValue initializer, the property
+  // If all property wrappers have a wrappedValue initializer, the property
   // wrapper will be initialized that way.
   return allAttachedPropertyWrappersHaveInitialValueInit();
 }

lib/SILGen/SILGen.cpp

@@ -1115,8 +1115,8 @@ emitStoredPropertyInitialization(PatternBindingDecl *pbd, unsigned i) {
             ->isPropertyMemberwiseInitializedWithWrappedType()) {
       auto wrapperInfo =
           originalProperty->getPropertyWrapperBackingPropertyInfo();
-      if (wrapperInfo.originalInitialValue)
-        init = wrapperInfo.originalInitialValue;
+      assert(wrapperInfo.originalInitialValue);
+      init = wrapperInfo.originalInitialValue;
     }
   }
 

lib/Sema/CodeSynthesis.cpp

@@ -145,7 +145,8 @@ static void maybeAddMemberwiseDefaultArg(ParamDecl *arg, VarDecl *var,
     var->getAttrs().hasAttribute<LazyAttr>() ||
     (!isExplicitlyInitialized && isDefaultInitializable &&
      var->getValueInterfaceType()->getAnyNominal() == ctx.getOptionalDecl() &&
-     !var->getAttachedPropertyWrapperTypeInfo(0).defaultInit);
+     (var->getAttachedPropertyWrappers().empty() ||
+      var->isPropertyMemberwiseInitializedWithWrappedType()));
   if (isNilInitialized) {
     arg->setDefaultArgumentKind(DefaultArgumentKind::NilLiteral);
     return;

lib/Sema/TypeCheckStorage.cpp

@@ -2436,8 +2436,7 @@ PropertyWrapperBackingPropertyInfoRequest::evaluate(Evaluator &evaluator,
   }
 
   // Get the property wrapper information.
-  if (!var->allAttachedPropertyWrappersHaveInitialValueInit() &&
-      !originalInitialValue) {
+  if (!var->allAttachedPropertyWrappersHaveInitialValueInit()) {
     return PropertyWrapperBackingPropertyInfo(
         backingVar, storageVar, nullptr, nullptr, nullptr);
   }

test/IDE/print_property_wrappers.swift

@@ -47,7 +47,7 @@ struct HasWrappers {
   var z: String
 
   // Memberwise initializer.
-  // CHECK: init(x: Wrapper<Int> = Wrapper(closure: foo), y: Bool = true, z: String = Wrapper())
+  // CHECK: init(x: Wrapper<Int> = Wrapper(closure: foo), y: Bool = true, z: Wrapper<String> = Wrapper())
 }
 
 func trigger() {